Optical circuit, and optical circuit device, sensor, and moving body employing same

Abstract

An optical circuit capable of reducing a frequency variation of a light source caused by rotation is provided. The optical circuit includes a substrate, a laser light source formed on the substrate and including a first annular optical waveguide and a second annular optical waveguide that shares a part thereof with the first annular optical waveguide at one location, a first optical waveguide located on the substrate at a position separated from the laser light source and optically coupled to the laser light source, and a resonator optically coupled to the first optical waveguide.

1 . An optical circuit comprising:
 a substrate;   a laser light source formed on the substrate and including a first annular optical waveguide and a second annular optical waveguide that shares a part thereof with the first annular optical waveguide at one location;   a first optical waveguide located on the substrate at a position separated from the laser light source and optically coupled to the laser light source; and   a resonator optically coupled to the first optical waveguide.   
     
     
         2 . The optical circuit as claimed in  claim 1 , wherein a ratio of a first area of a region surrounded by the first annular optical waveguide to a second area of a region surrounded by the second annular optical waveguide is between 0.5:1 and 2:1. 
     
     
         3 . The optical circuit as claimed in  claim 2 , wherein the first area and the second area are equal to each other. 
     
     
         4 . The optical circuit as claimed in  claim 1 , wherein the first annular optical waveguide and the second annular optical waveguide are formed of a semiconductor layered structure including a first semiconductor layer including a first impurity of a first conductivity type, an active layer provided on the first semiconductor layer, and a second semiconductor layer provided on the active layer and including a second impurity of a second conductivity type. 
     
     
         5 . The optical circuit as claimed in  claim 4 , wherein the laser light source and the first optical waveguide are parts of the semiconductor layered structure. 
     
     
         6 . The optical circuit as claimed in any one of  claims 1 to 5   claim 1 , further comprising:
 a second optical waveguide disposed on the substrate so as to be optically coupled to the laser light source;   an instrument configured to measure an intensity of light guided through the second optical waveguide; and   an intensity controller configured to perform a feedback to the laser light source so that the intensity of the light measured by the instrument becomes constant, wherein the second optical waveguide is disposed so that an optical coupling between the second optical waveguide and the laser light source is weaker than an optical coupling between the first optical waveguide and the laser light source.   
     
     
         7 . The optical circuit as claimed in  claim 1 , wherein the first optical waveguide is closest to one or both of the first annular optical waveguide and the second annular optical waveguide of the laser light source. 
     
     
         8 . The optical circuit as claimed in  claim 1 , wherein:
 the first optical waveguide includes a first optical coupler optically coupled to the first annular optical waveguide, and a second optical coupler optically coupled to the second annular optical waveguide,   a ratio of a magnitude of optical coupling at the first optical coupler to a magnitude of optical coupling at the second optical coupler is between 0.8:1 and 1.2:1, and   the first optical waveguide forms an open waveguide segment between the first optical coupler and the second optical coupler.   
     
     
         9 . The optical circuit as claimed in  claim 1 , wherein:
 the first optical waveguide includes a first branch configured to branch the light optically coupled to the laser light source at a ratio of 50:50,   the optical circuit includes a waveguide segment connected to the first branch, and   the resonator is optically coupled to the first optical waveguide at the waveguide segment.   
     
     
         10 . The optical circuit as claimed in  claim 1 , further comprising:
 a phase modulator provided between the laser light source and the resonator,   wherein a frequency of the laser light source matches one of a first resonance frequency of light that passes through the phase modulator and circulates in the resonator in a clockwise direction and a second resonance frequency of light that passes through the phase modulator and circulates in the resonator in a counterclockwise direction.   
     
     
         11 . An optical circuit device comprising:
 the optical circuit according to  claim 1 ;   a first instrument configured to detect first output light of the light circulating in the resonator in a first direction;   a second instrument configured to detect second output light of the light circulating in the resonator in a second direction opposite to the first direction; and   an electric circuit configured to control the optical circuit based on signals measured by the first instrument and the second instrument.   
     
     
         12 . A sensor comprising:
 the optical circuit according to  claim 1 ; and   a processor configured to process a measurement result of the output light of the optical circuit.   
     
     
         13 . A moving body comprising:
 the optical circuit according to  claim 1 .   
     
     
         14 . The optical circuit as claimed in  claim 3 , further comprising:
 a second optical waveguide disposed on the substrate so as to be optically coupled to the laser light source;   an instrument configured to measure an intensity of light guided through the second optical waveguide; and   an intensity controller configured to perform a feedback to the laser light source so that the intensity of the light measured by the instrument becomes constant,   wherein the second optical waveguide is disposed so that an optical coupling between the second optical waveguide and the laser light source is weaker than an optical coupling between the first optical waveguide and the laser light source.   
     
     
         15 . The optical circuit as claimed in  claim 3 , wherein:
 the first optical waveguide includes a first optical coupler optically coupled to the first annular optical waveguide, and a second optical coupler optically coupled to the second annular optical waveguide,   a ratio of a magnitude of optical coupling at the first optical coupler to a magnitude of optical coupling at the second optical coupler is between 0.8:1 and 1.2:1, and   the first optical waveguide forms an open waveguide segment between the first optical coupler and the second optical coupler.   
     
     
         16 . The optical circuit as claimed in  claim 14 , wherein:
 the first optical waveguide includes a first optical coupler optically coupled to the first annular optical waveguide, and a second optical coupler optically coupled to the second annular optical waveguide,   a ratio of a magnitude of optical coupling at the first optical coupler to a magnitude of optical coupling at the second optical coupler is between 0.8:1 and 1.2:1, and   the first optical waveguide forms an open waveguide segment between the first optical coupler and the second optical coupler.   
     
     
         17 . The optical circuit as claimed in  claim 3 , wherein:
 the first optical waveguide includes a first branch configured to branch the light optically coupled to the laser light source at a ratio of 50:50,   the optical circuit includes a waveguide segment connected to the first branch, and   the resonator is optically coupled to the first optical waveguide at the waveguide segment.   
     
     
         18 . A sensor comprising:
 the optical circuit device according to  claim 11 ; and   a processor configured to process a measurement result of the output light of the optical circuit.   
     
     
         19 . A moving body comprising:
 the optical circuit device according to  claim 11 .   
     
     
         20 . A moving body comprising:
 the sensor according to  claim 12 .